In a multiprogrammed system, when the operating system switches contexts, in addition to the cost for handling the processes being swapped out and in, the cache performance of processors also can be a€ected. If frequent context switching replaces the data loaded into cache memory before they are completely reused, the programs su€ffer from cache misses due to the damage in cache locality. In particular, for the programs with good cache locality, such as blocked programs, a scheduling mechanism of keeping cache locality against context switching is essential to achieve good processor utilization. To solve this requirement, we propose a preemption-safe policy to exploit the cache locality of blocked programs in a multiprogrammed system. The proposed policy delays context switching until a block is fully reused, but also compensates for the monopolized processor time on processor scheduling mechanisms. Our simulation results show that in a situation, where blocked programs are run on multiprogrammed shared-memory multiprocessors, the proposed policy improves the performance of these programs due to a decrease in cache misses. In such situations, it also has a bene®cial impact on the overall system performance due to the enhanced processor utilization.